The formation of cocrystals is currently receiving increased attention since they represent a class of materials with potential for exploitation to improve the physical or chemical properties of active pharmaceutical ingredients.1,2 While the uses of dry grinding, solvent drop grinding, and solvent crystallization have been reported as key preparative techniques,3-8 determination of the ternary phase diagram is likely to be an important aspect of the development of rational, large-scale preparative procedures using solution crystallization.9-12 In addition, such phase information can provide insights into the existence of metastable states and potential dissolution pathways